CVE-2023-46133: crypto-es PBKDF2 1,000 times weaker than specified in 1993 and 1.3M times weaker than current standard

Should you act?

Critical and remotely reachable

No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
• EPSS 0.4%, percentile 38: FIRST’s model estimates a 0.4% chance of exploitation activity in the next 30 days, higher than 38% of all scored CVEs (low). EPSS is a probability, not a verdict.
• Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
• Only applies if your dependency tree includes crypto-es (npm) < 2.1.0, fixed in 2.1.0. Check your lockfile, including transitive dependencies.

What it is

CryptoES is a cryptography algorithms library compatible with ES6 and TypeScript. Prior to version 2.1.0, CryptoES PBKDF2 is 1,000 times weaker than originally specified in 1993, and at least 1,300,000 times weaker than current industry standard. This is because it both defaults to SHA1, a cryptographic hash algorithm considered insecure since at least 2005, and defaults to one single iteration, a 'strength' or 'difficulty' value specified at 1,000 when specified in 1993. PBKDF2 relies on iteration count as a countermeasure to preimage and collision attacks. If used to protect passwords, the impact is high. If used to generate signatures, the impact is high. Version 2.1.0 contains a patch for this issue. As a workaround, configure CryptoES to use SHA256 with at least 250,000 iterations.

From the GitHub advisory

Impact Summary Crypto-js PBKDF2 is 1,000 times weaker than originally specified in 1993, and [at least 1,300,000 times weaker than current industry standard][OWASP PBKDF2 Cheatsheet]. This is because it both (1) defaults to [SHA1][SHA1 wiki], a cryptographic hash algorithm considered insecure [since at least 2005][Cryptanalysis of SHA-1] and (2) defaults to [one single iteration][one iteration src], a 'strength' or 'difficulty' value specified at 1,000 when specified in 1993. PBKDF2 relies on iteration count as a countermeasure to [preimage][preimage attack] and [collision][collision attack] attacks. Remediation of this issue might be very difficult, as the changes required to fix this issue would change the output of this method and thus break most, if not all, current uses of this method as configured by default.

Potential Impact:

1. If used to protect passwords, the impact is high. 2. If used to generate signatures, the impact is high.

Probability / risk analysis / attack enumeration:

1. [For at most $45,000][SHA1 is a Shambles], an attacker, given control of only the beginning of a crypto-js PBKDF2 input, can create a value which has identical cryptographic signature to any chosen known value. 4. Due to the [length extension attack] on SHA1, we can create a value that has identical signature to any unknown value, provided it is prefixed by a known value. It does not matter if PBKDF2 applies '[salt][cryptographic salt]' or '[pepper][cryptographic pepper]' or any other secret unknown to the attacker. It will still create an identical signature.

Weakness type: CWE-328, CWE-916, CWE-327.

Product: crypto-es (npm) · Assigned by: GitHub_M · Published: 2023-10-25

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: none (no login)
• User interaction: none
• Scope: unchanged

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation none, automatable yes, technical impact total.
• FIRST EPSS (model of 2026-10-21): 0.45% probability of exploitation activity in the next 30 days; percentile 38.

Timeline

• 2023-10-25 — CVE record published by GitHub_M
• 2023-10-25 — GitHub-reviewed advisory GHSA-mpj8-q39x-wq5h published (critical)
• 2024-09-10 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-mpj8-q39x-wq5h github.com
2. CVE.org record CVE-2023-46133 cve.org
3. NVD entry CVE-2023-46133 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com

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