VulnerabilityPublished 31 Oct 2026

CVE-2026-119197: Certsync · pyasn1 has quadratic-complexity denial of service in binary REAL decoding

Affects certsyncSource GCVE Database

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Mentioned vulnerabilities

CVE-2026-59886

Authoritative record:CVE-2026-119197· High 7.5

Not known to be exploited · CVSS 7.5 High · fixed in 0.6.5 : patch certsync soon.

Data as of 31 Oct 2026, 16:20 UTC

CVSS 3.1 base score

7.5High

How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none

CVSS scores by source
CNA (GitHub_M)	CVSS 3.1	7.5

Patch: Available – fixed in 0.6.5

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 29 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Homebrewcertsync`pkg:brew/certsync`Other threats	Affected >=0.1.4	Fixed in–

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AI-suggested

Upgrade pyasn1 to version 0.6.5 or later, which contains the official fix replacing the quadratic-time decoding loop with an efficient implementation. Until upgrading, applications should reject or strictly limit ASN.1 inputs containing REAL values, especially those with large mantissas, to reduce exposure to CPU exhaustion during decoding.

Description

pyasn1 versions up to 0.6.4 contain a denial of service vulnerability in the decoding of binary-encoded ASN.1 REAL values with large mantissas. The decoding process uses a quadratic-time algorithm that can exhaust CPU resources when processing attacker-controlled input. This affects BER, CER, and DER decoders that use the vulnerable RealPayloadDecoder. The issue is fixed in pyasn1 version 0.6.5.

Impact

An attacker able to supply ASN.1 input containing large binary REAL values to an application using pyasn1 up to version 0.6.4 can cause high CPU usage during decoding, potentially leading to denial of service by exhausting a CPU core. The vulnerability does not affect confidentiality or integrity and requires the attacker to control input passed to the decoder. There is no indication of network endpoint exposure or unauthenticated access inherent to the vulnerability itself.

Summary

In pyasn1 version 0.6.4 and earlier, the RealPayloadDecoder used for decoding binary-encoded ASN.1 REAL values builds the mantissa one octet at a time with a loop that shifts and slices the input bytes. This results in quadratic time complexity relative to the mantissa size, causing CPU exhaustion when decoding large mantissas. The vulnerability affects BER, CER, and DER decoders since they share the same REAL payload decoder. The issue is distinct from CVE-2026-59886 and does not require conversion or printing of the decoded REAL value to trigger. The vulnerability is present in all releases from v0.2.1 through v0.6.4. The fix in version 0.6.5 replaces the loop with a single int.from_bytes call, preserving decoding correctness while eliminating the performance issue.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 31 Oct 2026, 16:20 UTC

Technical details

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