Z.aiAnthropicTsinghua UniversityZhipu

Chinese AI startup Z.ai says open-source GLM-5.3 nears Anthropic's restricted Mythos 5 in finding software vulnerabilities; plans public release in two weeks

Chinese AI startup Z.ai announced that its open-source GLM-5.3 model is nearing Anthropic's restricted Mythos 5 in identifying software vulnerabilities, achieving an 84.5% score on CyberGym. The company plans to publicly release the model in two weeks, enhancing cybersecurity tools for developers and smaller teams.

Tech in Asia+1 source14 August 2026 · 11:05 UTC
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Chinese AI startup Z.ai has made significant strides with its open-source GLM-5.3 model, claiming it is close to matching Anthropic's Mythos 5 in software vulnerability detection. The model achieved an 84.5% score on CyberGym, surpassing Mythos 5's 83.8% score, although the results remain unverified.12345678

However, GLM-5.3 fell short in converting identified flaws into actionable attacks, scoring 54.4% on ExploitBench compared to Mythos 5's 78.0%. In timed tests, GLM-5.3 completed 105 attack-development tasks in two hours and 130 in six hours, while Mythos 5 completed 181 and 247 tasks, respectively.

Z.ai plans to publicly release GLM-5.3 in two weeks, following security assessments and enhancements to its safeguards. The company has implemented several protective measures, including systems to screen risky requests and monitor the model's outputs, aimed at distinguishing harmful activities from legitimate uses.

Z.ai positions this launch as a challenge to the restricted access of Mythos, advocating for the availability of advanced cyber-defense tools to open-source developers and smaller security teams. The company emphasizes that such tools should not be monopolized by a few closed-model providers, promoting a more inclusive approach to cybersecurity.

Key Insight
“GLM-5.3 scored 84.5% on CyberGym, edging Mythos 5's 83.8%, but lagged on ExploitBench (54.4% vs 78.0%). Z.ai will release weights publicly after security checks, with sensitive functions gated behind a 'trusted access' program.”
CuriousCats studied:
1
Tech in Asia
“Chinese AI startup , which evolved from Tsinghua University research, released on August 14.”
Tech in Asia →
2
CNBC TV18CNBC TV18
“Chinese AI startup Z.ai said on Friday (August 14) its open-source GLM-5.3 model had neared Anthropic’s restricted Mythos 5 in identifying software vulnerabilities, bolstering the credentials of a Chinese AI challenger gaining traction among Western developers.”
CNBC TV18 →
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