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CVE Record

CVE-2021-37606: Meow hash 0.5/calico does not sufficiently thwart key recovery by an attacker who can query whether there's...

Meow hash 0.5/calico does not sufficiently thwart key recovery by an attacker who can query whether there's a collision in the bottom bits of the hashes of two messages, as demonstrated by an attack against a long-running web service that allows the attacker to infer collisions by measuring timing differences.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

This CVE concerns a weakness in Meow hash 0.5/calico where an attacker may recover a secret key under narrow but serious conditions. The cited attack depends on a service that lets attackers submit chosen messages and infer partial hash collisions through timing differences.

Executive priority

Treat this as a targeted cryptographic design risk, not a broad mass-exploitation alert. Prioritize if Meow hash 0.5/calico protects secrets or integrity in externally reachable services. Otherwise, track as technical debt pending vendor guidance.

Technical view

The issue is described as insufficient resistance to key recovery when an attacker can query whether two messages collide in the low bits of their hashes. The public description cites a timing side channel in a long-running web service as the demonstration context. No CVSS, CWE, concrete vendor, product, or fixed version is provided.

Likely exposure

Exposure is most likely in custom software using Meow hash 0.5/calico for keyed or security-sensitive hashing, especially internet-facing services processing attacker-controlled messages. The source bundle does not identify packaged products, CPEs, or affected deployments.

Exploitation context

The CVE is not listed as KEV, and the bundle provides no evidence of active exploitation. The demonstrated scenario requires attacker-controlled queries plus an observable signal, such as timing, that reveals low-bit hash collisions.

Researcher notes

Evidence is narrow and incomplete: the CVE names Meow hash 0.5/calico and a timing-based key-recovery demonstration, but provides no CVSS, CWE, CPEs, affected product list, patch, or active exploitation signal. Validate usage context before assigning business impact.

Mitigation direction

  • Inventory use of Meow hash 0.5/calico in applications and libraries.
  • Check upstream or vendor guidance for supported fixes or replacement recommendations.
  • Avoid using Meow hash for authentication, integrity, or secret-bearing security decisions.
  • Review exposed services for timing-sensitive hash comparisons or collision-dependent behavior.
  • Prioritize replacement where attacker-controlled input reaches keyed hash logic.

Validation and detection

  • Search source and dependency manifests for Meow hash and calico references.
  • Identify whether any use is keyed or security-sensitive.
  • Confirm whether attackers can submit chosen messages to affected code paths.
  • Review logs and service design for timing-observable collision or comparison behavior.
  • Document any exposed deployment because public product mapping is incomplete.
Prepared
Confidence
medium
Sources
4

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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ATT&CK lookup starting points

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CVE-2021-37606 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
0Timeline events
0ADP providers
3Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.