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🛡️ OESA-2026-2079 — shim (CVE-2026-28388)

🟠 CVSS 8.0 — High ✅ No Known Exploit OSV
8.0
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

shim security update

Initial UEFI bootloader that handles chaining to a trusted full \ bootloader under secure boot environments.

Security Fix(es):

Issue summary: When a delta CRL that contains a Delta CRL Indicator extension

is processed a NULL pointer dereference might happen if the required CRL

Number extension is missing.

Impact summary: A NULL pointer dereference can trigger a crash which

leads to a Denial of Service for an application.

When CRL processing and delta CRL processing is enabled during X.509

certificate verification, the delta CRL processing does not check

whether the CRL Number extension is NULL before dereferencing it.

When a malformed delta CRL file is being processed, this parameter

can be NULL, causing a NULL pointer dereference.

Exploiting this issue requires the X509_V_FLAG_USE_DELTAS flag to be enabled in

the verification context, the certificate being verified to contain a

freshestCRL extension or the base CRL to have the EXFLAG_FRESHEST flag set, and

an attacker to provide a malformed CRL to an application that processes it.

The vulnerability is limited to Denial of Service and cannot be escalated to

achieve code execution or memory disclosure. For that reason the issue was

assessed as Low severity according to our Security Policy.

The FIPS modules in 3.6, 3.5, 3.4, 3.3 and 3.0 are not affected by this issue,

as the affected code is outside the OpenSSL FIPS module boundary.(CVE-2026-28388)

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 none, integrity none, availability high.

CVSS metrics in full

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

  • 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: None.
  • Integrity impact: None.
  • Availability impact: High — total loss, or loss the attacker controls.

Affected software

OESA-2026-2079 is recorded against 1 package.

  • shim (fixed in 15.6-30.oe2203sp4)

Timeline and source

Published on 25 April 2026 and last revised on 18 August 2026. No public exploit is currently recorded for this entry. Record sourced from OSV.

References

www.openeuler.org (Advisory)
nvd.nist.gov (Advisory)

Other advisories for this package

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

Details

Severity HIGH
CVSS Score 8.0
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE N/A
Public Exploit ✅ No
Source OSV
Published 2026-04-25
Updated 2026-08-20
Modified 2026-08-18
Fix URL N/A

Affected Packages

Software From version Fixed in
shim — 15.6-30.oe2203sp4

Similar Threats

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ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the vulnerabilities listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.

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