Security readout for executives and security teams
Plain-English summary
This weakness can let protected OpenPGP messages be recovered in specific ElGamal library interaction conditions. It affects confidentiality, not system takeover. The attack appears specialized and high-complexity, but the business concern is exposure of encrypted information if vulnerable Libgcrypt versions handled affected messages.
Executive priority
Treat this as a confidentiality-focused remediation item. It is not marked as known exploited in the provided evidence, but encrypted sensitive data could be exposed in affected OpenPGP ElGamal scenarios. Patch during the next security update cycle, sooner for high-sensitivity environments.
Technical view
Libgcrypt before 1.9.4 had an ElGamal implementation flaw involving receiver public-key parameters and sender ephemeral exponents. In a dangerous cross-library configuration, OpenPGP plaintext recovery may be possible. The CVE maps to CWE-327 and has CVSS 5.9 because confidentiality impact is high but attack complexity is high.
Likely exposure
Exposure is most likely where Libgcrypt before 1.9.4 is used for OpenPGP ElGamal operations. The provided affected-product metadata is incomplete, so teams should verify through package inventories, embedded dependencies, and distribution advisories rather than assuming only direct Libgcrypt installations matter.
Exploitation context
The source bundle does not show CISA KEV listing or active exploitation. The described attack requires a specific cryptographic parameter combination and cross-configuration behavior, so broad opportunistic exploitation is not established by the provided evidence.
Researcher notes
Focus validation on Libgcrypt version, OpenPGP ElGamal use, and cross-library interactions described by the IBM and IACR research. The provided bundle supports plaintext recovery risk but does not provide complete affected-product enumeration or evidence of active exploitation.
Mitigation direction
- Inventory systems and applications using Libgcrypt versions before 1.9.4.
- Upgrade Libgcrypt to 1.9.4 or vendor-supported fixed packages.
- Check distribution advisories for backported fixes and package-specific instructions.
- Prioritize systems handling sensitive OpenPGP ElGamal encrypted data.
- If upgrade is delayed, review vendor guidance for safe operational workarounds.
Validation and detection
- Confirm installed Libgcrypt versions across servers, workstations, containers, and bundled applications.
- Verify vendor package changelogs or advisories reference this CVE or the relevant fix.
- Identify whether OpenPGP ElGamal encryption workflows depend on vulnerable Libgcrypt builds.
- Review cryptographic services for cross-library OpenPGP processing paths.
- Document residual systems where version or ElGamal usage cannot be confirmed.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-327: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2021-40528 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 5.9 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N2.23.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
5.9MediumVector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://eprint.iacr.org/2021/923CVE reference
- https://ibm.github.io/system-security-research-updates/2021/07/20/insecurity-elgamal-pt1CVE reference
- https://ibm.github.io/system-security-research-updates/2021/09/06/insecurity-elgamal-pt2CVE reference
- https://git.gnupg.org/cgi-bin/gitweb.cgi?p=libgcrypt.git%3Ba=commit%3Bh=3462280f2e23e16adf3ed5176e0f2413d8861320CVE reference
- GLSA-202210-13CVE reference · vendor-advisory
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.