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🛡️ CVE-2026-31790 on Ubuntu — edk2

⚪ Unknown ✅ No Known Exploit OSV
N/A
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Issue summary: Applications using RSASVE key encapsulation to establish a secret encryption key can send contents of an uninitialized memory buffer to a malicious peer. Impact summary: The uninitialized buffer might contain sensitive data from the previous execution of the application process which leads to sensitive data leakage to an attacker. RSA_public_encrypt() returns the number of bytes written on success and -1 on error. The affected code tests only whether the return value is non-zero. As a result, if RSA encryption fails, encapsulation can still return success to the caller, set the output lengths, and leave the caller to use the contents of the ciphertext buffer as if a valid KEM ciphertext had been produced. If applications use EVP_PKEY_encapsulate() with RSA/RSASVE on an attacker-supplied invalid RSA public key without first validating that key, then this may cause stale or uninitialized contents of the caller-provided ciphertext buffer to be disclosed to the attacker in place of the KEM ciphertext. As a workaround calling EVP_PKEY_public_check() or EVP_PKEY_public_check_quick() before EVP_PKEY_encapsulate() will mitigate the issue. The FIPS modules in 3.6, 3.5, 3.4, 3.3, 3.1 and 3.0 are affected by this issue.

Distribution advisory

This page covers CVE-2026-31790 as tracked by Ubuntu, for the package edk2. The fix is available in version 3.5.5-1ubuntu3; earlier versions remain affected.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality high, integrity none, availability none.

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

  • Attack vector: Network — reachable from anywhere that can route to the service.
  • Attack complexity: Low — the attack works reliably, with no preparation.
  • Privileges required: None — an unauthenticated stranger can try it.
  • User interaction: None — nobody has to be tricked into anything.
  • Scope: Unchanged — the damage stays inside the vulnerable component.
  • Confidentiality impact: High — total loss, or loss the attacker controls.
  • Integrity impact: None.
  • Availability impact: None.

Weakness class

UBUNTU-CVE-2026-31790 is classified as CWE-754: Improper Check for Unusual or Exceptional Conditions. The product does not check or incorrectly checks for unusual or exceptional conditions that are not expected to occur frequently during day to day operation of the product.

Affected software

UBUNTU-CVE-2026-31790 is recorded against 3 packages.

  • edk2
  • openssl (fixed in 3.5.5-1ubuntu3)
  • openssl-fips

Timeline and source

Published on 7 April 2026 and last revised on 2 August 2026. No public exploit is currently recorded for this entry. Record sourced from OSV.

References

ubuntu.com (Report)
www.cve.org (Report)
www.openwall.com (Report)
ubuntu.com (Advisory)

Other advisories for this package

edk2 has other advisories on record. If you are patching this one, these are worth checking on the same host:

Same weakness in other software

These advisories are the same class of weakness (CWE-754: Improper Check for Unusual or Exceptional Conditions) in other software:

CVE-2026-31790 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity Unknown
CVSS Score N/A
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
CWE N/A
Public Exploit ✅ No
Source OSV
Published 2026-04-07
Updated 2026-08-20
Modified 2026-08-02
Fix URL N/A

Affected Packages

Software From version Fixed in
edk2 — —
openssl — 3.5.5-1ubuntu3
openssl-fips — —

Similar Threats

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