gcrymdblockwrite in cipher/hash-common.c in Libgcrypt version 1.9.0 has a heap-based buffer overflow when the digest final function sets a large count value. It is recommended to upgrade to 1.9.1 or later.

Libgcrypt before 1.8.1 does not properly consider Curve25519 side-channel attacks, which makes it easier for attackers to discover a secret key, related to cipher/ecc.c and mpi/ec.c.

cipher/elgamal.c in Libgcrypt through 1.8.2, when used to encrypt messages directly, improperly encodes plaintexts, which allows attackers to obtain sensitive information by reading ciphertext data (i.e., it does not have semantic security in face of a ciphertext-only attack). The Decisional Diffie-Hellman (DDH) assumption does not hold for Libgcrypt's ElGamal implementation.

GnuPG Libgcrypt could allow a remote attacker to obtain sensitive information, caused by improper handling of ElGamal encryption. By using side-channel attack techniques against mpipowm, and the window size, an attacker could exploit this vulnerability to obtain sensitive information, and use this information to launch further attacks against the affected system.

Last updated 25 August 2025

Last updated 27 May 2026

In Libgcrypt before 1.7.7, an attacker who learns the EdDSA session key (from side-channel observation during the signing process) can easily recover the long-term secret key. 1.7.7 makes a cipher/ecc-eddsa.c change to store this session key in secure memory, to ensure that constant-time point operations are used in the MPI library.

The ElGamal implementation in Libgcrypt before 1.9.4 allows plaintext recovery because, during interaction between two cryptographic libraries, a certain dangerous combination of the prime defined by the receiver's public key, the generator defined by the receiver's public key, and the sender's ephemeral exponents can lead to a cross-configuration attack against OpenPGP.

An implementation flaw was discovered in multiple cryptographic libraries that allows a side-channel based attacker to recover ECDSA or DSA private keys. When these cryptographic libraries use the private key to create a signature, such as for a TLS or SSH connection, they inadvertently leak information through memory caches. An unprivileged attacker running on the same machine can collect the information from a few thousand signatures and recover the value of the private key.

External References:

https://www.nccgroup.trust/us/our-research/technical-advisory-return-of-the-hidden-number-problem/

Last updated 27 May 2026

Libgcrypt before 1.12.2 sometimes allows a heap-based buffer overflow and denial of service via crafted ECDH ciphertext to gcrypkdecrypt.

The following announcement regarding libcrypt security releases was posted to gnupg-announce and related lists today. The forward is unedited except for trimming some footers inserted by mailing list software and the PGP/MIME signature.

----- Forwarded message from Werner Koch via Gnupg-devel <gnupg-devel () gnupg org> -----

Date: Tue, 21 Apr 2026 12:28:09 +0200 From: Werner Koch via Gnupg-devel <gnupg-devel () gnupg org> To: gnupg-announce () gnupg org Cc: Werner Koch <wk () gnupg org>, info-gnu () gnu org Subject: [Announce] [Security fixes] Libgcrypt 1.12.2, 1.11.3, 1.10.x released

Hello!

We are pleased to announce the availability of couple of new Libgcrypt versions: 1.12.2, 1.11.3, and 1.10.4 . It is suggested to use 1.12.2 which is fully compatible with all earlier versions.

This version fixes a security bug [T8211] which can be used used to mount a DoS using ECDH encryption (with NIST, Brainpool, X448, or X25519 curves). Note that GnuPG versions since 2.5.7 are not affected by this bug due to the use of a different encryption API.

Another security bug [T8208] was fixed in the Dilithium signing algorithm which is available since version 1.12.0.

Noteworthy changes in version 1.12.2 (2026-04-15) ====================================

Bug fixes:

- Fix possible ECDH buffer overwrite with zeroes. [T8211]

- Add a missing bounds check to the Dilithium context handling. Reported by Calif.io in collaboration with Claude and Anthropic Research. [T8208]

- Add point validation when using the new KEM interface. [T8212]

Other:

- Fix the dead-code of strongerkeycheck for RSA. [T8171]

For a list of links to commits and bug numbers see the release info at https://dev.gnupg.org/T8114 . However, due to an ongoing AI scraper DDoS the site might not be reachable at all times or from all IPs.

Noteworthy changes in version 1.11.3 (2026-04-21) ====================================

Bug fixes:

- Fix possible ECDH buffer overwrite with zeroes. [T8211]

- Add point validation when using the new KEM interface. [T8212]

- Fix compiler error on NetBSD. [T7633]

- mceliece6688128f: Fix stack overflow crash on win64/wine [rCb17ed8d1af]

- Apply a Kyber patch from upstream. [rC5ba143d51f]

- Use CSIDLCOMMONAPPDATA instead of /etc on Windows. [rC995b870fd2]

- Use secure MPI in gcrympiassignlimbspace. [rC520c699c82]

- Fix a regression with disabled public-key algo for FIPS. [T7338,rCc6e0658004]

Other:

- Handle HAVEBROKENMLOCK for the case of building with ASAN. [T7889]

- Add stack burning for PQC algorithms. [rC289c0a596f]

Release-info: https://dev.gnupg.org/T8232

Noteworthy changes in version 1.10.4 (2026-04-21) ====================================

NOTE: The 1.10 series reaches end-of-life in 6 weeks.

Bug fixes:

- Fix possible ECDH buffer overwrite with zeroes. [T8211]

- Fix AESWRAP padding length check. [T7130]

Other:

- Handle HAVEBROKENMLOCK for the case of building with ASAN. [T7889]

Release-info: https://dev.gnupg.org/T8233

Download ========

Source code is hosted at the GnuPG FTP server and its mirrors as listed at https://gnupg.org/download/mirrors.html. On the primary server the source tarball and its digital signature are:

https://gnupg.org/ftp/gcrypt/libgcrypt/libgcrypt-1.12.2.tar.bz2 https://gnupg.org/ftp/gcrypt/libgcrypt/libgcrypt-1.12.2.tar.bz2.sig https://gnupg.org/ftp/gcrypt/libgcrypt/libgcrypt-1.11.3.tar.bz2 https://gnupg.org/ftp/gcrypt/libgcrypt/libgcrypt-1.11.3.tar.bz2.sig https://gnupg.org/ftp/gcrypt/libgcrypt/libgcrypt-1.10.4.tar.bz2 https://gnupg.org/ftp/gcrypt/libgcrypt/libgcrypt-1.10.4.tar.bz2.sig

or gzip compressed:

https://gnupg.org/ftp/gcrypt/libgcrypt/libgcrypt-1.12.2.tar.gz https://gnupg.org/ftp/gcrypt/libgcrypt/libgcrypt-1.12.2.tar.gz.sig https://gnupg.org/ftp/gcrypt/libgcrypt/libgcrypt-1.11.3.tar.gz https://gnupg.org/ftp/gcrypt/libgcrypt/libgcrypt-1.11.3.tar.gz.sig https://gnupg.org/ftp/gcrypt/libgcrypt/libgcrypt-1.10.4.tar.gz https://gnupg.org/ftp/gcrypt/libgcrypt/libgcrypt-1.10.4.tar.gz.sig

In order to check that the version of Libgcrypt you downloaded is an original and unmodified file please follow the instructions found at https://gnupg.org/download/integritycheck.html. In short, you may use one of the following methods:

- Check the supplied OpenPGP signature. For example to check the signature of the file libgcrypt-1.12.2.tar.bz2 you would use this command:

gpg --verify libgcrypt-1.12.2.tar.bz2.sig libgcrypt-1.12.2.tar.bz2

This checks whether the signature file matches the source file. You should see a message indicating that the signature is good and made by one or more of the release signing keys. Make sure that this is a valid key, either by matching the shown fingerprint against a trustworthy list of valid release signing keys or by checking that the key has been signed by trustworthy other keys. See the end of this mail for information on the signing keys.

- If you are not able to use an existing version of GnuPG, you have to verify the SHA-1 checksum. On Unix systems the command to do this is either "sha1sum" or "shasum". Assuming you downloaded the file libgcrypt-1.12.2.tar.bz2, you run the command like this:

sha1sum libgcrypt-1.12.2.tar.bz2

and check that the output matches the first line from the this list:

7b8ff21966a0b6e7a735466b9b9b55d9dac9fa87 libgcrypt-1.12.2.tar.bz2 a1b1d5561e7b743e7e4460a49015053da1901124 libgcrypt-1.12.2.tar.gz d252f6b0a62fcacb8f82bcb61440b25d698a0a05 libgcrypt-1.11.3.tar.bz2 a89b597965a76bfbe0ad11e3d6153c3709c0b07e libgcrypt-1.11.3.tar.gz d824efa873ac210e84573564df4a99f4cd5cdf77 libgcrypt-1.10.4.tar.bz2 5a5bb8d4dd69a2c7828dbf31b12df5e21e604971 libgcrypt-1.10.4.tar.gz

You should also verify that the checksums above are authentic by matching them with copies of this announcement. Those copies can be found at other mailing lists, web sites, and search engines.

Copying =======

Libgcrypt is distributed under the terms of the GNU Lesser General Public License (LGPLv2.1+). The helper programs as well as the documentation are distributed under the terms of the GNU General Public License (GPLv2+). The file LICENSES has notices about contributions that require that these additional notices are distributed.

Support =======

For help on developing with Libgcrypt you should read the included manual and if needed ask on the gcrypt-devel mailing list.

In case of problems specific to this release please first check https://dev.gnupg.org/T8114 for updated information.

Please also consult the archive of the gcrypt-devel mailing list before reporting a bug: https://gnupg.org/documentation/mailing-lists.html . We suggest to send bug reports for a new release to this list in favor of filing a bug at https://bugs.gnupg.org. If you need commercial support go to https://gnupg.com or https://gnupg.org/service.html .

Please see https://gnupg.org/documentation/security.html for information on how to report security issues and for our threat model.

If you are a developer and you need a certain feature for your project, please do not hesitate to bring it to the gcrypt-devel mailing list for discussion.

Thanks ======

Since 2001 maintenance and development of GnuPG is done by g10 Code GmbH and has mostly been financed by donations. Several full-time employed developers and contractors are working exclusively on GnuPG and closely related software like Libgcrypt, GPGME, Kleopatra and Gpg4win.

Fortunately, and this is still not common with free software, we have now established a way of financing the development while keeping all our software free and freely available for everyone. Our model is similar to the way RedHat manages RHEL and Fedora: Except for the actual binary of the MSI installer for Windows and client specific configuration files, all the software is available under the GNU GPL and other Open Source licenses. Thus customers may even build and distribute their own version of the software as long as they do not use our trademarks GnuPG Desktop® or GnuPG VS-Desktop®.

We like to thank all the nice people who are helping the GnuPG project, be it testing, coding, translating, suggesting, auditing, administering the servers, spreading the word, answering questions on the mailing lists, or helping with donations.

Thank you all

Your Libgcrypt hackers

p.s. This is an announcement only mailing list. Please send replies only to the gcrypt-devel'at'gnupg.org mailing list.

List of Release Signing Keys: To guarantee that a downloaded version has not been tampered by malicious entities we provide signature files for all tarballs and binary versions. The keys are also signed by the long term keys of their respective owners. Current releases are signed by one or more of these five keys:

ed25519 2020-08-24 [SC] [expires: 2030-06-30] 6DAA 6E64 A76D 2840 571B 4902 5288 97B8 2640 3ADA Werner Koch (dist signing 2020)

ed25519 2021-05-19 [SC] [expires: 2027-04-04] AC8E 115B F73E 2D8D 47FA 9908 E98E 9B2D 19C6 C8BD Niibe Yutaka (GnuPG Release Key)

rsa3072 2025-05-09 [SC] [expires: 2033-03-03] 3B76 1AE4 E63B F351 9CE7 D63B ECB6 64CB E133 2EEF Alexander Kulbartsch (GnuPG Release Key)

brainpoolP256r1 2021-10-15 [SC] [expires: 2029-12-31] 02F3 8DFF 731F F97C B039 A1DA 549E 695E 905B A208 GnuPG.com (Release Signing Key 2021)

brainpoolP384r1 2026-02-23 [SC] [expires: 2034-02-23] 1493 269D E61F 124A A69A 316E 3ADF 34EB DBB2 00A4 GnuPG.com (Release Signing Key 2026)

The keys are available at https://gnupg.org/signaturekey.html and in any recently released GnuPG tarball in the file g10/distsigkey.gpg . Note that this mail has been signed by a different key.

Debian Package Signing Key: The new Debian style packages are signed using this key:

ed25519 2025-07-08 [SC] [expires: 2035-07-14] 3209 7B71 9B37 45D6 E61D DA1B 85C4 5AE3 E1A2 B355 GnuPG.org Package Signing Key <package-maintainers () gnupg org>

See the package website (https://repos.gnupg.org/deb/gnupg) for a list of supported distributions and a download link for the key.

-- The pioneers of a warless world are the youth that refuse military service. - A. Einstein

----- End forwarded message -----