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Denial of service via attribute length limit bypass

CVE-2026-128085GHSA-Q7GW-24FR-5P69

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

5.3MediumCNA
Exploited
No known exploitation
Fix
Fixed in 1.47.0
Who is exposed
Not reported

Do first: Upgrade to a fixed version: 1.47.0.

Published
Last modified
Reference
Last checked
0.47% · 41st percentile
32/100 · provisional
None on Exploit-DB, Metasploit or GitHub

Summary

The opentelemetry-go SDK (go.opentelemetry.io/otel/sdk) fails to enforce its attribute value length limit for values made of or dominated by valid U+FFFD replacement characters. An attacker can exploit this remotely, without logging in, by sending telemetry attributes that exceed the configured bound, which increases retained memory and pipeline pressure but does not affect confidentiality or integrity.

Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.

Original description

OpenTelemetry-Go is the Go implementation of OpenTelemetry. From SDK version 1.33.0, SDK log version 0.9.0, and trace version 1.35.0 until version 1.47.0, the AttributeValueLengthLimit and WithAttributeValueLengthLimit truncation paths in sdk/internal/attrnorm, sdk/log/internal/attrnorm, and trace/auto.go do not count valid U+FFFD replacement characters. This is a distinct incomplete-fix defect in the replacement truncation code introduced by the remediation for CVE-2026-81869. Values composed of or dominated by those characters can therefore exceed the configured character and memory bound in span, log-record, and auto-instrumentation trace attributes. Attacker-controlled telemetry attributes can increase retained memory and pipeline pressure, while confidentiality and integrity are not affected. This issue is fixed in version 1.47.0.

cve.now Index

32Pcve.now Index 32 of 100 · methodology v3 · provisional
  • Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
  • Exposure17/25No login or user action needed per the CVSS vector, reachable over the network without a login · Unknown: No advisory context yet
  • Reach10/20Affects Go packages
  • Severity5.3/10CVSS 5.3
  • No patch0/5No signal

What would change the score

  • Would score about 77 if added to CISA KEV
  • Would score about 72 if CISA's SSVC rates exploitation active
  • Would score about 37 if advisories confirm default setups are exposed

How the score works · Rankings

What to do

  • Upgrade to a fixed version: 1.47.0.

Check your systems with an agent

Paste this into a coding or ops agent. It checks your systems read-only and reports a table per asset.

Check whether my systems are affected by CVE-2026-128085 (opentelemetry-go: AttributeValueLengthLimit is fully bypassed by attribute values composed of valid U+FFFD runes), using the cve.now data below.

Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only.

What cve.now has for CVE-2026-128085 (entry last updated 2026-11-13):
Affected:
- open-telemetry opentelemetry-go: from 0.9.0, fixed in 1.47.0
- open-telemetry go.opentelemetry.io/otel/sdk: from 1.33.0, fixed in 1.47.0
- open-telemetry go.opentelemetry.io/otel/sdk: from 0.9.0, fixed in 1.47.0
- open-telemetry go.opentelemetry.io/otel/sdk: from 1.35.0, fixed in 1.47.0
- Go package go.opentelemetry.io/otel/sdk: from 1.33.0, fixed in 1.47.0
- Go package go.opentelemetry.io/otel/sdk/log: from 0.9.0, fixed in 1.47.0
- Go package go.opentelemetry.io/otel/trace: from 1.35.0, fixed in 1.47.0
Fixed versions: 1.47.0.
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
CISA KEV: CVE-2026-128085 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-128085 only. If you also check another CVE, look up its own KEV status; never assume it from this one.

How to check:
- Packages (Go): find every lockfile in each project and run the stack.check operation of the cve.now MCP server (execute) on each one. Compare the resolved versions, not the ranges a manifest declares, with the affected versions above. Include transitive dependencies.
- Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory.

Verify against the linked advisories before concluding, and cite the date you read each one:
- https://github.com/open-telemetry/opentelemetry-go/security/advisories/GHSA-q7gw-24fr-5p69
- https://github.com/open-telemetry/opentelemetry-go/commit/017b08c7f1018b619991aaf6b2299d4beb9da1d3
- https://github.com/open-telemetry/opentelemetry-go/releases/tag/sdk/log/v1.47.0
- https://github.com/open-telemetry/opentelemetry-go/releases/tag/sdk/v1.47.0
- https://github.com/open-telemetry/opentelemetry-go/releases/tag/trace/v1.47.0
Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing.

Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action.

Entry: https://cve.now/CVE-2026-128085
For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example execute with name cve.get and arguments {"id": "CVE-2026-128085"}.

Timeline

  1. CVE published
  2. First seen by cve.now

Affected versions

  • open-telemetry opentelemetry-go

    From 0.9.0 · fixed in 1.47.0

  • open-telemetry go.opentelemetry.io/otel/sdk

    From 1.33.0 · fixed in 1.47.0

  • open-telemetry go.opentelemetry.io/otel/sdk

    From 0.9.0 · fixed in 1.47.0

  • open-telemetry go.opentelemetry.io/otel/sdk

    From 1.35.0 · fixed in 1.47.0

  • From 1.33.0 · fixed in 1.47.0

    Fixed in v1.47.0 (released Oct 2, 2026, 42 days before disclosure).

    The latest release, v1.47.0, is not affected.

  • From 0.9.0 · fixed in 1.47.0

    Fixed in v1.47.0 (released Oct 2, 2026, 42 days before disclosure).

    The latest release, v1.47.0, is not affected.

  • From 1.35.0 · fixed in 1.47.0

    Fixed in v1.47.0 (released Oct 2, 2026, 42 days before disclosure).

    The latest release, v1.47.0, is not affected.

Evidence 7

Vendor advisory · 1

Establishes: Affected and fixed versions.

  1. Advisory

CVE record · 2

Establishes: The identifier and description.

  1. Record
  2. Record

Other links · 4

  1. Repository
  2. Repository
  3. Repository
  4. Repository

Corrections

None so far.

Something wrong on this page? Report an error. Every fix is listed here.

Questions about CVE-2026-128085

Is CVE-2026-128085 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data

Which versions are affected by CVE-2026-128085?

opentelemetry-go: from 0.9.0 before 1.47.0. go.opentelemetry.io/otel/sdk: from 1.33.0 before 1.47.0. go.opentelemetry.io/otel/sdk: from 0.9.0 before 1.47.0. go.opentelemetry.io/otel/sdk: from 1.35.0 before 1.47.0. go.opentelemetry.io/otel/sdk (Go): from 1.33.0 before 1.47.0. 2 more packages are listed on the page.Source: cve.now feed data

How do I fix CVE-2026-128085?

Upgrade to a fixed version: 1.47.0.Source: cve.now feed data

Sources

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