CVE-2026-50012
Description
A flaw was found in Squid. Due to improper input validation, a heap-based buffer overflow can occur when processing cache digests. This issue allows a trusted server to cause a denial of service when sending specially crafted replies to cache_digest request messages.
Statement
To exploit this issue, an attacker must control a trusted cache peer server. Also, cache digests are not enabled in the default configuration. Squid deployments that do not use cache peering are not affected. Furthermore, even those that do are only vulnerable when the attacker controls a configured peer server within the same administrative domain. A compromised peer can reliably crash the Squid process via a heap-based buffer overflow during digest exchange, but code execution faces considerable practical security barriers.
Default Red Hat Enterprise Linux security features, including SELinux enforcement, Address Space Layout Randomization (ASLR) and NX (No-Execute) stack protection, significantly increase the difficulty of achieving arbitrary code execution, limiting the impact of this vulnerability.
Due to these reasons, this vulnerability has been rated with a moderate severity.
Mitigation
To mitigate this vulnerability, restrict or disable cache digest processing for cache peers by adding the appropriate settings to the squid.conf configuration file:
Disable cache digests for any cache_peer not under direct control by adding the no-digest option. This completely removes the vulnerability for those peers at the cost of increased bandwidth. Use of HTCP or ICP as alternative protocols can reduce that cost.
# Example of disabling digests for an untrusted peer.
cache_peer untrusted.server.example.com parent 3128 3130 no-digest
Audit the Squid configuration and ensure that all configured cache_peer entries are under direct control and are trusted. Restricting cache peering exclusively to trusted domains greatly reduces the risk of exploitation.
# Example of a fully trusted peer without the no-digest flag.
cache_peer trusted.internal.example.com parent 3128 3130
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.5 | 5.5 | 5.5 |
| Attack Vector | Network | Network | Network |
| Attack Complexity | Low | Low | Low |
| Privileges Required | High | High | High |
| User Interaction | None | None | None |
| Scope | Unchanged | Unchanged | Unchanged |
| Confidentiality | None | None | None |
| Integrity Impact | Low | Low | Low |
| Availability Impact | High | High | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:L/A:H
NVD: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:L/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:L/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory)
Buffer overflows generally lead to crashes. Other attacks leading to lack of availability are possible, including putting the program into an infinite loop.
Integrity,Confidentiality,Availability,Access Control
Technical Impact: Execute Unauthorized Code or Commands; Bypass Protection Mechanism; Modify Memory
Buffer overflows often can be used to execute arbitrary code, which is usually outside the scope of a program's implicit security policy. Besides important user data, heap-based overflows can be used to overwrite function pointers that may be living in memory, pointing it to the attacker's code. Even in applications that do not explicitly use function pointers, the run-time will usually leave many in memory. For example, object methods in C++ are generally implemented using function pointers. Even in C programs, there is often a global offset table used by the underlying runtime.
Integrity,Confidentiality,Availability,Access Control,Other
Technical Impact: Execute Unauthorized Code or Commands; Bypass Protection Mechanism; Other
When the consequence is arbitrary code execution, this can often be used to subvert any other security service.
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