A security regression (CVE-2006-5051) was discovered in OpenSSH's server (sshd). There is a race condition which can lead sshd to handle some signals in an unsafe manner. An unauthenticated, remote attacker may be able to trigger it by failing to authenticate within a set time period.
In the Linux kernel, the following vulnerability has been resolved:
In the Linux kernel, the following vulnerability has been resolved:
A vulnerability was found in GNU Nano that allows a possible privilege escalation through an insecure temporary file. If Nano is killed while editing, a file it saves to an emergency file with the permissions of the running user provides a window of opportunity for attackers to escalate privileges through a malicious symlink.
A vulnerability was found in GnuTLS. The response times to malformed ciphertexts in RSA-PSK ClientKeyExchange differ from the response times of ciphertexts with correct PKCS#1 v1.5 padding. This issue may allow a remote attacker to perform a timing side-channel attack in the RSA-PSK key exchange, potentially leading to the leakage of sensitive data. CVE-2024-0553 is designated as an incomplete resolution for CVE-2023-5981.
A heap use-after-free issue has been identified in SQLite in the jsonParseAddNodeArray() function in sqlite3.c. This flaw allows a local attacker to leverage a victim to pass specially crafted malicious input to the application, potentially causing a crash and leading to a denial of service.
A flaw was found in m2crypto. This issue may allow a remote attacker to decrypt captured messages in TLS servers that use RSA key exchanges, which may lead to exposure of confidential or sensitive data.
Last updated 24 September 2025
Summary
Terrapin is a prefix truncation attack targeting the SSH protocol. More precisely, Terrapin breaks the integrity of SSH's secure channel. By carefully adjusting the sequence numbers during the handshake, an attacker can remove an arbitrary amount of messages sent by the client or server at the beginning of the secure channel without the client or server noticing it.
Mitigations
To mitigate this protocol vulnerability, OpenSSH suggested a so-called "strict kex" which alters the SSH handshake to ensure a Man-in-the-Middle attacker cannot introduce unauthenticated messages as well as convey sequence number manipulation across handshakes.
Warning: To take effect, both the client and server must support this countermeasure.
As a stop-gap measure, peers may also (temporarily) disable the affected algorithms and use unaffected alternatives like AES-GCM instead until patches are available.
Details
The SSH specifications of ChaCha20-Poly1305 (chacha20-poly1305@openssh.com) and Encrypt-then-MAC (-etm@openssh.com MACs) are vulnerable against an arbitrary prefix truncation attack (a.k.a. Terrapin attack). This allows for an extension negotiation downgrade by stripping the SSHMSGEXTINFO sent after the first message after SSHMSGNEWKEYS, downgrading security, and disabling attack countermeasures in some versions of OpenSSH. When targeting Encrypt-then-MAC, this attack requires the use of a CBC cipher to be practically exploitable due to the internal workings of the cipher mode. Additionally, this novel attack technique can be used to exploit previously unexploitable implementation flaws in a Man-in-the-Middle scenario.
The attack works by an attacker injecting an arbitrary number of SSHMSGIGNORE messages during the initial key exchange and consequently removing the same number of messages just after the initial key exchange has concluded. This is possible due to missing authentication of the excess SSHMSGIGNORE messages and the fact that the implicit sequence numbers used within the SSH protocol are only checked after the initial key exchange.
In the case of ChaCha20-Poly1305, the attack is guaranteed to work on every connection as this cipher does not maintain an internal state other than the message's sequence number. In the case of Encrypt-Then-MAC, practical exploitation requires the use of a CBC cipher; while theoretical integrity is broken for all ciphers when using this mode, message processing will fail at the application layer for CTR and stream ciphers.
For more details see https://terrapin-attack.com.
Impact
This attack targets the specification of ChaCha20-Poly1305 (chacha20-poly1305@openssh.com) and Encrypt-then-MAC (-etm@openssh.com), which are widely adopted by well-known SSH implementations and can be considered de-facto standard. These algorithms can be practically exploited; however, in the case of Encrypt-Then-MAC, we additionally require the use of a CBC cipher. As a consequence, this attack works against all well-behaving SSH implementations supporting either of those algorithms and can be used to downgrade (but not fully strip) connection security in case SSH extension negotiation (RFC8308) is supported. The attack may also enable attackers to exploit certain implementation flaws in a man-in-the-middle (MitM) scenario.
crypto: algifaead - Revert to operating out-of-place
Last updated 30 June 2026
A heap-buffer-overread vulnerability exists in GnuTLS (confirmed in version 3.8.9) due to unsafe handling of the Certificate Transparency (CT) Signed Certificate Timestamp (SCT) extension during X.509 certificate parsing. The vulnerability can be triggered by a malicious peer presenting a crafted certificate containing a malformed SCT extension (OID 1.3.6.1.4.1.11129.2.4.2). This overread may lead to disclosure of heap memory contents to attackers if the SCT logid is logged, exported, or otherwise exposed by the application consuming the GnuTLS client library.
A double-free vulnerability exists in GnuTLS (confirmed in version 3.8.9) due to incorrect ownership handling in the export logic of Subject Alternative Name (SAN) entries containing an otherName. If the type-id OID is invalid or malformed, GnuTLS will call asn1deletestructure() on an ASN.1 node it does not own, leading to a double-free condition when the parent function or caller later attempts to free the same structure. This vulnerability can be triggered using only public GnuTLS APIs and may result in denial of service or memory corruption, depending on allocator behavior.
A vulnerability was found in OpenSSH when the VerifyHostKeyDNS option is enabled. A machine-in-the-middle attack can be performed by a malicious machine impersonating a legit server. This issue occurs due to how OpenSSH mishandles error codes in specific conditions when verifying the host key. For an attack to be considered successful, the attacker needs to manage to exhaust the client's memory resource first, turning the attack complexity high.
A race condidition in systemd-coredump allows a local attacker to crash a SUID program and gain read access to the resulting core dump
A flaw was found in rsvpchange(). The root cause is an slab-out-of-bound access, but since the offset to the original pointer is an unsign int fully controlled by users, the behavior is usually a wild pointer access.
A flaw was found in ipv4senddestunreach() due to NULL pointer derefence due to a missing edge-case check.
An array indexing vulnerability was found in the netfilter subsystem of the Linux kernel. A missing macro could lead to a miscalculation of the h->nets array offset, providing attackers with the primitive to arbitrarily increment/decrement a memory buffer out-of-bound. This issue may allow a local user to crash the system or potentially escalate their privileges on the system.
A flaw was found in the XFRM subsystem in the Linux kernel. The specific flaw exists within the processing of state filters, which can result in a read past the end of an allocated buffer. This flaw allows a local privileged (CAPNETADMIN) attacker to trigger an out-of-bounds read, potentially leading to an information disclosure.
A flaw was found in the Netfilter subsystem in the Linux kernel. The sctpmtcheck did not validate the flagcount field. This flaw allows a local privileged (CAPNETADMIN) attacker to trigger an out-of-bounds read, leading to a crash or information disclosure.
A flaw was found in the Netfilter subsystem in the Linux kernel. The xtu32 module did not validate the fields in the xtu32 structure. This flaw allows a local privileged attacker to trigger an out-of-bounds read by setting the size fields with a value beyond the array boundaries, leading to a crash or information disclosure.
A flaw was found in the Netfilter subsystem in the Linux kernel. The nfnlosfaddcallback function did not validate the user mode controlled optnum field. This flaw allows a local privileged (CAPNETADMIN) attacker to trigger an out-of-bounds read, leading to a crash or information disclosure.
In the Linux kernel through 6.3.1, a use-after-free in Netfilter nftables when processing batch requests can be abused to perform arbitrary read and write operations on kernel memory. Unprivileged local users can obtain root privileges. This occurs because anonymous sets are mishandled.
HTTP/2 Rapid reset attack The HTTP/2 protocol allows clients to indicate to the server that a previous stream should be canceled by sending a RSTSTREAM frame. The protocol does not require the client and server to coordinate the cancellation in any way, the client may do it unilaterally. The client may also assume that the cancellation will take effect immediately when the server receives the RSTSTREAM frame, before any other data from that TCP connection is processed.
Abuse of this feature is called a Rapid Reset attack because it relies on the ability for an endpoint to send a RSTSTREAM frame immediately after sending a request frame, which makes the other endpoint start working and then rapidly resets the request. The request is canceled, but leaves the HTTP/2 connection open.
The HTTP/2 Rapid Reset attack built on this capability is simple: The client opens a large number of streams at once as in the standard HTTP/2 attack, but rather than waiting for a response to each request stream from the server or proxy, the client cancels each request immediately.
The ability to reset streams immediately allows each connection to have an indefinite number of requests in flight. By explicitly canceling the requests, the attacker never exceeds the limit on the number of concurrent open streams. The number of in-flight requests is no longer dependent on the round-trip time (RTT), but only on the available network bandwidth.
In a typical HTTP/2 server implementation, the server will still have to do significant amounts of work for canceled requests, such as allocating new stream data structures, parsing the query and doing header decompression, and mapping the URL to a resource. For reverse proxy implementations, the request may be proxied to the backend server before the RSTSTREAM frame is processed. The client on the other hand paid almost no costs for sending the requests. This creates an exploitable cost asymmetry between the server and the client.
Multiple software artifacts implementing HTTP/2 are affected. This advisory was originally ingested from the swift-nio-http2 repo advisory and their original conent follows.
swift-nio-http2 specific advisory swift-nio-http2 is vulnerable to a denial-of-service vulnerability in which a malicious client can create and then reset a large number of HTTP/2 streams in a short period of time. This causes swift-nio-http2 to commit to a large amount of expensive work which it then throws away, including creating entirely new Channels to serve the traffic. This can easily overwhelm an EventLoop and prevent it from making forward progress.
swift-nio-http2 1.28 contains a remediation for this issue that applies reset counter using a sliding window. This constrains the number of stream resets that may occur in a given window of time. Clients violating this limit will have their connections torn down. This allows clients to continue to cancel streams for legitimate reasons, while constraining malicious actors.
An Out-Of-Bounds Read vulnerability in smbCalcSize in fs/smb/client/netmisc.c in the Linux Kernel. This flaw could allow a local attacker to crash the system or leak internal kernel information.
Refer; https://bugzilla.kernel.org/showbug.cgi?id=218218
[1] Retrieve WordCount and add offset2 to the data part of smb [2] Retrieve a 16-byte value from the calculated pointer
c unsigned int smbCalcSize(void buf) { struct smbhdr ptr = buf; return (sizeof(struct smbhdr) + (2 ptr->WordCount) + 2 / size of the bcc field / + getbcc(ptr)); } ... static inline u16 getbcc(struct smbhdr hdr) { le16 bcptr = (le16 )BCC(hdr);
return getunalignedle16(bcptr);//[2] } ... static inline void BCC(struct smbhdr smb) { return (void )smb + sizeof(smb) + 2 smb->WordCount; //[1] }
[2] cifsdemultiplexthread → standardreceive3 → cifshandlestandard → checkSMB → smbCalcSize
c int checkSMB(char buf, unsigned int totalread, struct TCPServerInfo server) { struct smbhdr smb = (struct smbhdr )buf; u32 rfclen = be32tocpu(smb->smbbuflength); u32 clclen; / calculated length / cifsdbg(FYI, "checkSMB Length: 0x%x, smbbuflength: 0x%x\n", totalread, rfclen);
/ is this frame too small to even get to a BCC? / if (totalread < 2 + sizeof(struct smbhdr)) { ... }
/ otherwise, there is enough to get to the BCC / if (checksmbhdr(smb)) return -EIO; clclen = smbCalcSize(smb);
An out-of-bounds read issue was found in the NVMe-oF/TCP subsystem in the Linux kernel. A remote attacker could send a crafted TCP packet triggering a heap-based buffer overflow that results in kmalloc data to be printed (and potentially leaked) to the kernel ring buffer (dmesg).
Upstream refs: https://lore.kernel.org/linux-nvme/b58a2dc6-cc8f-4d19-9efe-e1d5b4505efc@nvidia.com/T/ https://lore.kernel.org/linux-nvme/CAK5usQvxAyC3LJ4OnqerS1P0JpbfFr9uRZmq6Jb4QhaB7AQCoQ@mail.gmail.com/T/
A use-after-free vulnerability was found in drivers/nvme/target/tcp.c in nvmettcpfreecrypto due to a logical bug in the NVMe-oF/TCP subsystem in the Linux kernel. In this flaw, a malicious user can cause a UAF and a double free, which may lead to RCE (may also lead to an LPE in case the attacker already has local privileges).
Reference: https://lore.kernel.org/linux-nvme/20231002105428.226515-1-sagi@grimberg.me/
A flaw has been identified in glibc. In an uncommon situation, the gaihinet function may use memory that has been freed, resulting in an application crash. This issue is only exploitable when the getaddrinfo function is called and the hosts database in /etc/nsswitch.conf is configured with SUCCESS=continue or SUCCESS=merge.
A flaw was found in the GNU C Library. A recent fix for CVE-2023-4806 introduced the potential for a memory leak, which may result in an application crash.
A buffer overflow was discovered in the GNU C Library's dynamic loader ld.so while processing the GLIBCTUNABLES environment variable. This issue could allow a local attacker to use maliciously crafted GLIBCTUNABLES environment variables when launching binaries with SUID permission to execute code with elevated privileges.