CVE-2020-13784Network attack vector

Session hijacking via time-seeded random values

Published Jun 3, 2020 · Updated Aug 4, 2024

Predictable PRNG seeding in D-Link DIR-865L Ax 1.20B01 Beta allows remote attackers to derive encrypted session cookies from login times. The get_random_string function seeds its generator with the login-attempt time, making its cookie, challenge, and public-key outputs predictable. Knowledge of the approximate login time is sufficient to recover session information and bypass the protection provided by HTTPS.

CVSS severity7.5
High
EPSS probability1.30%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Predictable PRNG seeding in D-Link DIR-865L Ax 1.20B01 Beta allows remote attackers to derive encrypted session cookies from login times. The get_random_string function seeds its generator with the login-attempt time, making its cookie, challenge, and public-key outputs predictable. Knowledge of the approximate login time is sufficient to recover session information and bypass the protection provided by HTTPS.

The record

CVE
CVE-2020-13784
Published
Jun 3, 2020
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-337, CWE-335, T1550.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 3, 2020CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.0NIST NVDAV:N/AC:L/Au:N/C:P/I:N/A:N
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-337Predictable Seed in Pseudo-Random Number Generator
CWE-335Incorrect Usage of Seeds in Pseudo-Random Number Generator (PRNG)
T1550.004Use Alternate Authentication Material: Web Session Cookie

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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