HIGH 7.5 Microsoft PoC
CVE-2021-33560
Libgcrypt before 1.8.8 and 1.9.x before 1.9.3 mishandles ElGamal encryption because it lacks exponent blinding to address a side-channel attack against mpi_powm and the window size is not chosen appropriately. This for example affects use of ElGamal in OpenPGP.
Microsoft Security Update 2026-Aug: Libgcrypt before 1.8.8 and 1.9.x before 1.9.3 mishandles ElGamal encryption because it lacks exponent blinding to address a side-channel attack against mpi_powm and the window size is not chosen appropriately. This for example affects use of ElGamal in OpenPGP.
Affected Products
- cm1 libgcrypt 1.8.7-2 on CBL Mariner 1.0
- azl3 grub2 2.06-23 on Azure Linux 3.0
References
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-33560
- https://nvd.nist.gov/vuln/detail/CVE-2021-33560
This high severity vulnerability with a CVSS score of 7.5 was published on 2026-08-06 via Microsoft. 🚨 A public proof-of-concept exploit is available on GitHub. Affected: cm1 libgcrypt 1.8.7-2 on CBL Mariner 1.0, azl3 grub2 2.06-23 on Azure Linux 3.0.
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