VulnerabilityPublished 28 Oct 2026Updated 29 Oct 2026

CVE-2026-53939: cjose security update

Affects cjoseSource GCVE Database

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Authoritative record:CVE-2026-53939· Critical 9.1

Not known to be exploited · CVSS 9.1 Critical : upgrade to 0.6.1-17.el9_8.2 as a priority.

Data as of 30 Oct 2026, 01:32 UTC

CVSS 3.1 base score

9.1Critical

How severe the flaw is on the 0–10 CVSS scale.

Patch: Available – fixed in 0.6.1-17.el9_8.2

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: High
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 9 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

almalinux-9

What to do

Upgrade the AlmaLinux to 0.6.1-17.el9_8.2.

Patches and advisories

access.redhat.com/errata/RHSA-2026:92145 (opens in a new tab)

Affected software

Product	Affected	Fixed in
AlmaLinux 9cjose	Affected <0.6.1-17.el9_8.2	Fixed in 0.6.1-17.el9_8.2
AlmaLinux 9cjose-devel	Affected <0.6.1-17.el9_8.2	Fixed in 0.6.1-17.el9_8.2

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A security update fixing this vulnerability is available in cjose version 0.6.1-17.el9_8.2. Users should apply this update promptly. Refer to the Red Hat advisory RHSA-2026:92145 and the update instructions at https://access.redhat.com/articles/11258 for detailed remediation steps.

Description

CJose, a C library implementing Javascript Object Signing and Encryption (JOSE), contains a critical vulnerability (CVE-2026-53939) where it uses an all-zero Content Encryption Key for AES-CBC-HMAC JWE encryption. This flaw compromises the encryption process, potentially allowing attackers to bypass confidentiality protections. A security update fixing this issue is available in version 0.6.1-17.el9_8.2 and later.

Impact

The vulnerability allows the use of a predictable all-zero encryption key in AES-CBC-HMAC JWE encryption, which can lead to compromised confidentiality of encrypted data. This significantly weakens the cryptographic protection provided by cjose, potentially enabling attackers to decrypt or tamper with protected information.

Summary

The vulnerability in cjose (CVE-2026-53939) involves the use of an all-zero Content Encryption Key for AES-CBC-HMAC JSON Web Encryption (JWE). This cryptographic flaw undermines the security guarantees of the encryption scheme, potentially exposing sensitive data. The issue affects versions prior to 0.6.1-17.el9_8.2. Red Hat has issued a critical security advisory and released a patch to address this vulnerability.

References

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