CVE-2026-56851: 
New Relic Agent vulnerability analysis and mitigation

CVE-2026-56851 is a denial-of-service vulnerability in the golang.org/x/text/secure/precis Go package, specifically affecting the Nickname profile transformation function. When processing crafted input into a short destination buffer, the Nickname profile can trigger a panic due to an out-of-bounds slice error. All versions of golang.org/x/text/secure/precis prior to 0.41.0 are affected. The vulnerability was published on October 7, 2026, with a patch released in version 0.41.0. It carries a CVSS v3.1 base score of 7.5 (High) (GitHub Advisory).

The root cause is classified as CWE-787 (Out-of-bounds Write): the Nickname profile's transformation logic writes or accesses data beyond the bounds of a short destination buffer when processing specially crafted input strings. The attack vector is network-based, requires no authentication or user interaction, and has low attack complexity, making it straightforward to trigger remotely. An attacker simply needs to supply a crafted string to any application endpoint that passes input through the precis Nickname profile transformation. Relevant upstream references include the Go issue tracker and code review (Go Issue, Go CL, Go Vuln DB).

Successful exploitation causes the affected Go application to panic and crash, resulting in a denial of service. The impact is limited to availability — there is no confidentiality or integrity impact, as the vulnerability does not expose data or allow unauthorized modification. Any application that uses the golang.org/x/text/secure/precis Nickname profile to process untrusted input is at risk of being remotely crashed by an unauthenticated attacker (GitHub Advisory).

There is no public proof-of-concept exploit and no evidence of in-the-wild exploitation at this time (GitHub Advisory). The vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog. The EPSS score is approximately 0.155% (0.00155), indicating a low probability of exploitation in the near term. However, the attack is classified as automatable with no privileges or user interaction required, meaning exploitation could be straightforward once a viable payload is identified.

1. Reconnaissance: Identify applications built with Go that use golang.org/x/text/secure/precis versions prior to 0.41.0, particularly those exposing endpoints that accept user-supplied strings processed through the Nickname profile (e.g., username normalization, XMPP, or similar identity fields).
2. Craft malicious input: Construct a string payload designed to trigger the out-of-bounds slice condition when the Nickname profile attempts to transform it into a short destination buffer. The exact payload characteristics are not publicly documented, but the trigger involves input that causes the transformation to exceed buffer bounds.
3. Submit payload: Send the crafted input to the target application via any network-accessible interface (e.g., HTTP API, login form, registration endpoint) that passes the value through the precis.Nickname.Transform() or equivalent function.
4. Trigger panic: The application's Go runtime encounters the out-of-bounds slice access and panics, crashing the process or goroutine and causing a denial of service (Go Issue, GitHub Advisory).

• Logs: Application logs showing unexpected Go runtime panic messages such as runtime error: slice bounds out of range or panic: runtime error originating from golang.org/x/text/secure/precis stack frames.
• Process: Sudden, repeated crashes or restarts of Go application processes, particularly correlated with incoming network requests containing unusual string inputs.
• Network: Repeated requests to endpoints that handle username or nickname normalization, especially with non-standard Unicode or specially encoded string values.

The fix is available in golang.org/x/text version 0.41.0 and later; upgrading to this version is the recommended remediation (GitHub Advisory, Go Vuln DB). For teams unable to patch immediately, implementing input validation or size limits on strings processed through the Nickname profile can reduce exposure by preventing crafted payloads from reaching the vulnerable code path. Developers should audit all usages of precis.Nickname in their codebases and ensure dependencies are updated.

The vulnerability was included in Microsoft's October 2026 Patch Tuesday coverage, which addressed a record 1,411 flaws (BleepingComputer). Tenable published detection plugins for the vulnerability. No significant independent researcher commentary or social media discussion has been identified beyond standard aggregator coverage.